In recent years, electrically rewritable nonvolatile semiconductor memory devices have become indispensable in redundancy rescue of large-capacity memory devices such as DRAM and SRAM, tuning of analog circuits, storage of chip ID, and so on.
In order to provide the above-mentioned nonvolatile semiconductor memory devices at a cheap price, there is need of a storage element mountable only by a CMOS standard process. An antifuse element is a storage element that fulfills such a requirement.
An antifuse element includes a gate oxidation film. The antifuse element is in a high-resistance state when the gate oxidation film is intact, and stores this state as data “0”. Moreover, the antifuse element attains a low-resistance state due to the gate oxidation film being destroyed, and stores this state as data “1”. For example, a write operation is executed by applying a high voltage to the gate oxidation film thereby destroying the gate oxidation film. Further, a read operation is executed by applying to the gate oxidation film a voltage insufficient for the gate oxidation film to be destroyed and detecting a current flowing in the antifuse element.
However, power consumption in the write operation and read operation of the antifuse element is not sufficiently suppressed, neither is operation speed sufficiently increased.